岩石矿物学杂志2018，Vol.37Issue(2)：270-280,11.
东天山大草滩蛇纹岩中铬铁矿特征及其构造意义
Characteristics and tectonic significance of chromites from Dacaotan serpentinite of East Tianshan Mountains
摘要
Abstract
The disseminated and banded chromites in the serpentinized ultrabasic rocks of the Dacaotan area,East Tianshan Mountains,are helpful to clarifying the characteristics and evolutionary process of the rocks.Some chromites have zoned texture,with rich A1 but poor Fe in the core.The geochemical characteristics of the core of chromites,with the data Cr2O3 39.27％ ～42.65％,Al2O3 24.58％ ～26.21％,TiO2 less than 0.20％,FeO 12.18％ ～18.14％,Fe2O3 0.33％ ～7.30％,Cr# 50.6 ～53.5,Mg# 53.3 ～68.2,and Fe2+#31.8 ～46.7,are in accord with the features of ophiolites serpentinite and may be a member of ophiolites.Moreover,the crystallization temperature and pressure of the chromite are estimated to be 1 385℃ and 2.77 GPa on average,respectively,with a formation depth of about 86 km,which is similar to features of the asthenosphere.The oxygen fugacity relative to FMQ buffer is FMQ-4.38 ～ FMQ + 0.63 log units,FMQ-1.15 log units on average.Furthermore,the degree of partial melting of the mantle is estimated to be in the range of 21.04％ ～ 21.28％,21.18％ on average,in the light of its relationship with Cr#.These parameters provide some clues to the physicochemical conditions:these peridotites were derived from garnet lherzolites located in the asthenosphere of the upper mantle,and Dacaotan serpentinite was formed in the depleted island-arc setting of supra-subduction zone.The compositional zoning suggests that the peridotites have undergone a thermal path of decreasing temperature and increasing oxygen fugacity.It can be inferred that the mantle peridotites experienced the process from the stage of high temperature and high pressure mantle with lower oxygen fugacity to the thrusting slice stage to reach the crustal surface,where they were subjected to regional metamorphism with higher oxygen fugacity.关键词
铬铁矿/蛇绿岩/蛇纹岩/构造环境/大草滩/东天山Key words
chromite/ophiolite/serpentinite/tectonic setting/Dacaotan/East Tianshan Mountains分类
天文与地球科学引用本文复制引用
王成,田江涛,李大海,唐毅..东天山大草滩蛇纹岩中铬铁矿特征及其构造意义[J].岩石矿物学杂志,2018,37(2):270-280,11.基金项目
中央返还两权价款项目(T15-2-LQ13) （T15-2-LQ13）
新疆区域地质调查片区总结与服务产品开发项目(DD20160345-04) Two Right Cost Budget Project(T15-2-LQ13) （DD20160345-04）
Summary of Regional Geological Surveys in Xinjiang and Development of Its Service Products (DD20160345-04) （DD20160345-04）
